/*******************************************************************************
 * Copyright 2011 Mauro Luigi Drago (drago.luigi@gmail.com)
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *******************************************************************************/
package com.bytenose.extrautils.patterns.observer;

import com.bytenose.extrautils.annotations.NonNullable;

/**
 * Provides a mechanism for receiving push-based notifications.
 * This interface is copied from the Microsoft .NET 4 platform.  
 * @author Mauro Luigi Drago
 *
 * @param <T> The object that provides notification information.
 */
public interface IObserver<T> {
	
	/**
	 * Notifies the observer that the provider has finished sending push-based notifications.
	 */
	void onCompleted();
	
	/**
	 * Notifies the observer that the provider has experienced an error
	 * condition.
	 * @param error 
	 * 		an object that provides additional information about the error, cannot be null
	 * @throws IllegalArgumentException 
	 * 		if some of the {@link NonNullable} arguments are null.
	 */
	void onError(@NonNullable Exception error) 
		throws IllegalArgumentException;
	
	/**
	 * Provides the observer with new data.
	 * @param value the current notification information, cannot be null.
	 * @throws IllegalArgumentException 
	 * 		if some of the {@link NonNullable} arguments are null.
	 */
	void onNext(@NonNullable T value)
		throws IllegalArgumentException;
}
